U.S. patent number 5,451,752 [Application Number 08/357,010] was granted by the patent office on 1995-09-19 for noise shielding apparatus for magnetron of microwave oven.
This patent grant is currently assigned to Daewoo Electronics Co., Ltd.. Invention is credited to Jaewon Cho, Wonpyo Hong, Wookeum Jun, Heungdae Kang, Byeongjun Kim, Sangjin Kim, Byungkap Lim.
United States Patent |
5,451,752 |
Jun , et al. |
September 19, 1995 |
Noise shielding apparatus for magnetron of microwave oven
Abstract
A noise shielding apparatus for the magnetron of a microwave
oven for preventing the lowering of the voltage resistance of the
capacitor due to the poor concentricity and the poor interfacial
state is disclosed. A shielding case has a side wall with an
elliptic opening and a projected portion along the elliptic opening
by bending out a circumference portion thereof. The capacitor
includes an elliptic cylindrical ceramic dielectric, separate
electrodes separately formed on an upper surface of the ceramic
dielectric and a common electrode formed on a lower surface of the
ceramic dielectric. Through conductors pass through the through
holes and are connected to a choke coil of the magnetron. Each of
through conductors is provided with an electrode connection portion
for electrically connecting with the separate electrodes integrally
and horizontally formed from around an upper portion of each of
through conductors. An insulation lattice is formed at a central
upper portion of the insulation case over a border line of the
separate electrodes. Forming the electrode connection portion
prevents the poor perpendicularity and/or poor interfacial state.
Providing the insulation lattice solves simply and stably the
insulation problem between fastening tabs and thus the magnetron
may be stably operated.
Inventors: |
Jun; Wookeum (Incheon,
KR), Kim; Byeongjun (Incheon, KR), Hong;
Wonpyo (Kyungki-Do, KR), Kim; Sangjin (Incheon,
KR), Lim; Byungkap (Seoul, KR), Kang;
Heungdae (Incheon, KR), Cho; Jaewon (Seoul,
KR) |
Assignee: |
Daewoo Electronics Co., Ltd.
(Seoul, KR)
|
Family
ID: |
26630398 |
Appl.
No.: |
08/357,010 |
Filed: |
December 16, 1994 |
Foreign Application Priority Data
|
|
|
|
|
May 27, 1994 [KR] |
|
|
94-11651 |
Jun 28, 1994 [KR] |
|
|
94-15055 |
|
Current U.S.
Class: |
219/761; 219/738;
315/39.51; 361/302 |
Current CPC
Class: |
H01G
4/35 (20130101); H01J 23/15 (20130101); H05B
6/66 (20130101); H05B 6/76 (20130101); H01R
13/719 (20130101) |
Current International
Class: |
H01J
23/15 (20060101); H01J 23/00 (20060101); H05B
6/76 (20060101); H01R 13/719 (20060101); H01B
006/64 (); H01G 004/42 () |
Field of
Search: |
;219/761,736,738
;361/302,330 ;315/39.51,39.53 ;174/35R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Leung; Philip H.
Attorney, Agent or Firm: Lowe, Price, LeBlanc &
Becker
Claims
What is claimed is:
1. A noise shielding apparatus for a magnetron, comprising:
a shielding case having an elliptic opening on a side wall thereof
and a projected portion formed along said elliptic opening by
bending out a circumference portion of said elliptic opening, and a
recess formed on an inner surface thereof corresponding to said
projected portion;
an elliptic cylindrical ceramic dielectric having a size
corresponding to said elliptic opening of said shielding case, and
having a pair of through holes;
a pair of separate electrodes separately formed on an upper surface
of said ceramic dielectric;
a common electrode formed on a lower surface of said ceramic
dielectric and oppositely from said separate electrodes;
a pair of through conductors passing through said through holes and
to be connected to a choke coil of the magnetron, each of said
through conductors being provided with an electrode connection
portion for electrically connecting with said separate electrodes,
said electrode connection portion being integrally and horizontally
formed from around an upper portion of each of said through
conductors;
an insulation case with a lower portion secured on said projected
portion of said shielding case for surrounding said ceramic
dielectric; and
an elliptic insulation cylinder with its upper portion secured in
said recess of said shielding case for surrounding said through
conductors.
2. The noise shielding apparatus as claimed in claim 1, wherein
said electrode connection portion is formed in a ring shape along a
periphery of each of said through conductors by horizontally
extending from each of said through conductors.
3. The noise shielding apparatus as claimed in claim 2, wherein a
recessed portion is formed on a bottom of said electrode connection
portion for stably filling into said through holes, said recessed
portion being formed between each of said through conductors and an
outer periphery of said electrode connection portion.
4. The noise shielding apparatus as claimed in claim 3, said noise
shielding apparatus further comprising a bending portion at the
outer periphery of said electrode connection portion for increasing
a contact area between said electrode connection portion and said
separate electrodes and for improving a stable perpendicularity of
said through conductors.
5. The noise shielding apparatus as claimed in claim 1, said noise
shielding apparatus further comprising an insulation lattice formed
at a central upper portion of said insulation case over a border
line of said separate electrodes.
6. The noise shielding apparatus as claimed in claim 1, said noise
shielding apparatus further comprising a rib formed around said
projected portion on said shielding case for reinforcing a strength
of said shielding case.
7. The noise shielding apparatus as claimed in claim 1, said noise
shielding apparatus further comprising a first insulation resin
material filled within said insulation case so as to surround said
ceramic dielectric.
8. The noise shielding apparatus as claimed in claim 1, said noise
shielding apparatus further comprising a second insulation resin
filled in an upper portion of said insulation cylinder so as to
surround said through conductors.
9. The noise shielding apparatus as claimed in claim 1, said noise
shielding apparatus further comprising fastening tabs formed on an
upper portion of each of said through conductors for being
connected to an external terminal, and said fastening tabs being
extended outside of said insulation case.
10. The noise shielding apparatus as claimed in claim 1, said noise
shielding apparatus further comprising a pair of insulation tubes
surrounding a pair of said through conductors, respectively.
11. A noise shielding apparatus for a magnetron, comprising:
a shielding case having an elliptic opening on a side wall thereof
and a projected portion formed along said elliptic opening by
bending out a circumference portion of said elliptic opening, and a
recess formed on an inner surface thereof corresponding to said
projected portion;
an elliptic cylindrical ceramic dielectric having a size
corresponding to said elliptic opening of said shielding case, and
having a pair of through holes;
a pair of separate electrodes separately formed on an upper surface
of said ceramic dielectric;
a common electrode formed on a lower surface of said ceramic
dielectric and oppositely from said separate electrodes;
a pair of through conductors passing through said through holes and
to be connected to a choke coil of the magnetron, each of said
through conductors being provided with an electrode connection
portion for electrically connecting with said separate electrodes,
said electrode connection portion being integrally and horizontally
formed from around an upper portion of each of said through
conductors, said electrode connection portion having a recessed
portion formed on a bottom of said electrode connection portion for
stably filling into said through holes, said recessed portion being
formed between each of said through conductors and an outer
periphery of said electrode connection portion;
an insulation case with a lower portion secured on said projected
portion of said shielding case for surrounding said ceramic
dielectric;
an elliptic insulation cylinder with its upper portion secured in
said recess of said shielding case for surrounding said through
conductors;
a first insulation resin material filled within said insulation
case so as to surround said ceramic dielectric;
a second insulation resin filled in an upper portion of said
insulation cylinder so as to surround said through conductors;
fastening tabs formed on an upper portion of each of said through
conductors for being connected to an external terminal, and said
fastening tabs being extended outside of said insulation case;
and
a pair of insulation tubes surrounding a pair of said through
conductors, respectively.
12. The noise shielding apparatus as claimed in claim 11, wherein
said insulation tubes are buried with said second insulation resin
material.
13. The noise shielding apparatus as claimed in claim 11, said
noise shielding apparatus further comprising an insulation lattice
formed at a central upper portion of said insulation case over a
border line of said separate electrodes.
14. The noise shielding apparatus as claimed in claim 13, wherein a
lower end of said insulation lattice is buried with said first
insulation resin material.
15. The noise shielding apparatus as claimed in claim 13, wherein
said insulation lattice is formed between a pair of said fastening
tabs so as to have an upper end with a height higher than a height
of said fastening tabs.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a noise shielding apparatus in
which a noise generated in a magnetron of a microwave oven can be
effectively shielded. More particularly, the present invention
relates to a noise shielding apparatus in which the structure of
the shielding apparatus is simple, but the performance is very
high, so that the productivity can be improved, and that the
overall manufacturing cost can be saved. The present invention is
an improvement over the invention which is the subject matter of
one of the present inventor's co-pending U.S. patent application
Ser. No. 08/307,129 filed on Sep. 16, 1994 (European Patent
Application No. 94 114 731.6 filed on Sep. 19, 1994), the
disclosure of which is hereby incorporated into this application by
reference.
2. Prior Arts
Generally, various apparatuses such as home microwave ovens,
commercial thawing apparatuses, industrial driers and the like
using microwaves are provided with a magnetron for generating
microwaves, and a capacitor for shielding noises.
In an electric field room of a microwave oven, there is provided a
magnetron for generating microwaves. Such microwaves are generated
when a high voltage produced by primary and secondary induction
coils of a high voltage transformer which is attached on a base
plate of the electric field room, is stably supplied to the
magnetron, the high voltages being generated through the inductive
interaction between the induction coils. Such microwaves are
irradiated into a cooking chamber through an irradiating tube.
When the microwaves are irradiated into the cooking chamber after
passing through the irradiating tube, the food placed within the
cooking chamber is heated so as to be cooked.
The power supply line of the magnetron mainly consists of a
filament, a cathode and an anode. When the high voltage is supplied
to the magnetron to generate microwaves, unnecessarily radiated
microwaves, i.e., noises are generated, besides microwaves having
basic frequencies which are suitable for heating the food. Then,
the noises flow back through the filament and the cathode so as to
cause wave obstructions in the nearby apparatuses.
Particularly, coming recently, television broadcasts resorting to
satellites are widely utilized. The unnecessary microwaves of the
magnetron interacts with the broadcasting frequencies and therefore
there is a possibility that receiving disorders may occur on a
television receiver.
In order to reduce such adverse influences given to the nearby
apparatuses due to the magnetron noise, a choke coil and a
capacitor connected thereto are provided on the cathode which
supplies power to the filament. The choke coil which has a
reactance, and the capacitor which is connected to the choke coil
absorb the unnecessary microwaves, thereby blocking the leakage of
the unnecessary microwaves.
The choke coil is sealed within a shielding case which is provided
under the magnetron, while the capacitor is installed on the
outside of the shielding case. One end of the choke coil is
connected to the power supply line of the filament, while the other
end is connected to a lead line of the capacitor.
The widely used capacitor is a through-type, and such a
through-type capacitor is described in U.S. Pat. No. 4,811,161
(issued to Sasaki et al). In the magnetron using the through-type
capacitor, the choke coil is connected in series between the
cathode of the magnetron and a through conductor of the
through-type capacitor which is inserted in a side wall of the
shielding case.
FIG. 1 is an exploded perspective view of a noise shielding
apparatus including a conventional through-type capacitor 30 and
FIG. 2 is a front sectional view of through-type capacitor 30 of
FIG. 1.
As shown in the drawings, the conventional through-type capacitor
30 includes an elliptic ceramic dielectric 32. Ceramic dielectric
32 is provided with a pair of vertical through holes 34 which are
formed in parallel with each other. On the upper surface of ceramic
dielectric 32, there are provided a pair of electrodes 36 which are
separated from each other, while a common electrode 38 is provided
on the lower surface of ceramic dielectric 32. Separate electrodes
36 and common electrode 38 are provided with through holes
corresponding to through hole 34 of ceramic dielectric 32.
Capacitor 30 further includes a ground fitment 40 made of a metal
in which an elliptic opening 42 is formed at a center portion
thereof, on which there is formed an upstand 44 along the
circumference of opening 42 with a suitable height. Ceramic
dielectric 32 is fixed via common electrode 38 on upstand 44 of
ground fitment 40 by a proper means such as soldering or the
like.
Further, capacitor 30 includes a pair of through conductors 46 each
covered with an insulation tube 48, insulation tube 48 being formed
of a suitable material such as silicon. Insulation tubes 48 are
inserted into through holes 34, and opening 42 and through
conductors 46 each are fittedly secured in an electrode connectors
50 each of which is fixed on separate electrodes 36 by a proper
means such as soldering or the like. Fixing of through conductors
46 to electrode connectors 50 may be carried out by soldering or
the like.
Ground fitment 40 is formed by pressing a metal plate in such a
manner that upstand 44 should surround opening 42 in a projected
contour, and that the other side of ground fitment 40 is provided
with a recess 52 so as to form the inner surface of upstand 44. At
the four corner portions of ground fitment 40, there are formed
four piercing holes 41, so that ground fitment 40 may be attached
to a shielding case (which is also called a "filter box") 90.
Capacitor 30 further includes an insulation case 54 which surrounds
ceramic dielectric 32 and an insulation cylinder 56 which surrounds
through conductors 46. The lower portion of insulation case 54 is
secured to upstand 44 of ground fitment 40, while the upper portion
of insulation cylinder 56 is secured by recess 52 of ground fitment
40. Insulation case 54 and insulation cylinder 56 are filled with a
first and second insulation resin materials 58 and 60 comprised of
an insulation material such as an epoxy resin or the like so as to
cover an outside and inside of ceramic dielectric 32 with the resin
or embed it therein to thereby ensure moisture proofness and
insulation properties of ceramic electric. Insulation case 54 and
insulation cylinder 56 are made of a thermoplastic resin such as
polybutylene terepthalate (PBT).
Each of through conductors 46 is integrally provided with a
fastening tab 62 on one end thereof which is to be received into
insulation case 54 for applying a high voltage. One end of
fastening tab 62 projects from one end of insulation case 54, so
that the tab can be easily connected to an external terminal.
When ground fitment 40 is fixedly secured on shielding case 90,
shielding case 90 is provided with a large hole 91 corresponding to
the capacitor and four bearing holes 92 corresponding to four
piercing holes 41 of ground fitment 40. Then bearing holes 92 and
piercing holes 41 are matched to assemble them using bolts or a
caulking process.
FIG. 3 is a partial sectional view for illustrating a magnetron
having a conventional through-type capacitor. In the drawing,
reference numeral 500 denotes a magnetron for generating a
microwave, reference numeral 501 denotes an antenna rod, reference
numeral 502 denotes a cathode stem, reference numeral 503 denotes a
cathode terminal and reference numeral 504 denotes a choke coil
wound on an inductor. Choke coil 504 is connected in series between
cathode terminal 503 and through conductors 46 of capacitor 30.
When a microwave noise which is generated from magnetron 500 flows
in reverse, the microwave noise passes through choke coil 504 via
cathode terminal 503 which is connected to the filament of
magnetron 500, with the result that a portion of the noise is
offset owing to the reactance of choke coil 504. The rest of the
microwave noise passes through through conductors 46 which are
connected to choke coil 504, and during this passing, a portion
thereof is dissipated by through-type capacitor 30 which includes
ceramic dielectric 32 (in which through conductors 46 are
inserted). The last remaining portion of the noise is completely
dissipated by being grounded to shielding case 90 which is
connected with common electrode 38.
Through-type capacitor 30 which connects choke coil 504 of the
interior of shielding case 90 with an external terminal inhibits
the conducting noise from conducting through the lead, and also
shields a radiating noise. However, as shown in the drawings, the
conventional noise shielding apparatus of a magnetron includes many
components assembled together, and therefore, not only the
structure is complicated so as to increase the material cost, but
also the assembling process is very fastidious so as to lower the
productivity. Further, after the assembling, a considerable amount
of radiating waves is leaked through insertion hole 91 of shielding
case 90, holes 41 of ground fitment 40 and burring holes 92 of
shielding case 90, with the result that the shielding of the noise
cannot be maximized.
FIGS. 4A and 4B are a partial front view and a partial sectional
side view for explaining the noise leakage in a noise shielding
apparatus having a conventional through-type capacitor. As shown in
FIG. 4B, it can be seen that a noise such as unnecessary radiating
wave 400 which flows in reverse to cathode terminal 503 of
magnetron 500 leaks through burring holes 92 or the gap formed by
the interface between shielding case 90 and ground fitment 40.
In the meantime, Wookeum Jun, one of the present inventors
suggested an integral capacitor of a magnetron for a microwave oven
which has a relatively simple structure to reduce the material cost
and to improve the productivity. The capacitor is disclosed in an
U.S. patent application Ser. No. 08/307,129 filed on Sep. 16, 1994
(European Patent Application No. 94 114 731.6 filed on Sep. 19,
1994), which is now pending.
FIG. 5 is an exploded perspective view of a capacitor disclosed in
the above U.S. patent application and FIG. 6 is a front sectional
view of the noise shielding apparatus of FIG. 5.
A through-type capacitor 130 as shown in FIGS. 5 and 6 is similar
to the conventional capacitor. Capacitor 130 includes an elliptic
ceramic dielectric 132, and ceramic dielectric 132 is provided with
a pair of vertical through holes 134 which are substantially
parallel with each other. Further, a pair of mutually separate
electrodes 136 are provided on the top of ceramic dielectric 132,
while a common electrode 138 is provided on the bottom of the
ceramic dielectric 132. Separate electrodes 136 and common
electrode 138 are provided with through holes corresponding to
through holes 134 of ceramic dielectric 132.
Capacitor 130 is secured to a shielding case 100 which is provided
with an elliptic opening 111 at a center portion of a side wall
thereof for receiving capacitor 130. Further, an opening 200 is
formed at a center portion of an upper portion of shielding case
100 for receiving the cathode of a magnetron, while the lower
portion of shielding case 100 is totally open. A projected portion
110 is formed with a proper height around opening 11 by
protrudingly bending a circumference portion of opening 111. On an
inner surface portion of shielding case 100, a recess 113 is formed
corresponding to projected portion 110. Around projected portion
110 and on the surface portions of shielding case 100, there are
formed reinforcing ribs 112 for reinforcing the strength of
shielding case 100.
Ceramic dielectric 132 is secured to projected portion 110 of
shielding case 100 by fixing common electrode 138 to projected
portion 110 by a proper means such as soldering or the like.
Capacitor 130 includes a pair of through conductors 146 each
surrounded by an insulation tube 148 which is made of a proper
material such as silicon. Through conductors 146 are disposed at a
center portion of shielding case 100, and are connected to a choke
coil which is connected to the filament of the magnetron,
connecting through conductors 146 with the filament being made by a
proper means such as soldering or the like. Insulation tubes 148
are inserted into through holes 134, and opening 111 and through
conductors 146 are fixed to electrode connectors 150 which are
secured on separate electrodes 136. Fixing through conductors 146
on electrode connectors 150 can be performed by a proper means such
as soldering or the like.
Capacitor 130 also includes an insulation case 154 and an
insulation cylinder 156. The lower portion of insulation case 154
which surrounds ceramic dielectric 132 is secured on projected
portion 110, while the upper portion of insulation cylinder 156
which surrounds through conductors 146 is secured in recess 113 of
shielding case 100. Insulation case 154 and insulation cylinder 156
are filled with an insulation resin such as an epoxy resin so as to
cover an outside and inside of ceramic dielectric 132 to thereby
ensure its moisture proofness and its insulation properties.
Insulation case 154 and insulation cylinder 156 are formed of a
thermoplastic resin such as PBT.
Each of through conductors 146 is integrally provided with a
fastening tab 162 to which a high voltage is applied. Fastening tab
162 is received into insulation case 154, so that an end portion of
fastening tab 162 would project from insulation case 154, thereby
making it easy to be connected to an external terminal.
In the case where the above noise shielding apparatus is used, if a
microwave noise which is generated from the magnetron flows in
reverse, the microwave noise passes through a choke coil (not
shown) which is connected to the filament of the magnetron, with
the result that a portion of the noise is offset owing to the
reactance of the choke coil. The rest of the microwave noise passes
through through conductors 146 which are connected to the choke
coil, and during this passing, a portion thereof is dissipated by
capacitor 130 which includes ceramic dielectric 132 (in which
through conductors 146 are inserted). The last remaining portion of
the noise is completely dissipated by being grounded to shielding
case 100 which is connected with the common electrode 138.
In the above capacitor, shielding case 100 is punched and bent so
as to form the projected portion 110 around opening 111. Projected
portion 110 performs the role of the conventional ground fitment
(40 in FIG. 1) which is fixedly installed on the shielding
case.
Since projected portion 110 effectively performs the role of the
conventional ground fitment 40, a separate ground fitment is
unnecessary. Therefore, the material cost is saved, and a working
process for installing ground fitment 40 is unnecessary, thereby
improving the productivity.
Further, the microwave noise which is generated by the magnetron is
continuously dissipated by the ceramic dielectric during passing
through through conductors 146 which are inserted in ceramic
dielectric 132. Then, the noise is completely dissipated by being
grounded to shielding case 100 which is connected to common
electrode 138. In the above capacitor, when compared to a
conventional capacitor, projected portion 110 which performs the
role of the conventional ground fitment is integrally formed on
shielding case 100. Therefore, the surface of common electrode 138
of ceramic dielectric 132 directly contacts with the surface of
projected portion 110, and therefore, the grounding resistance is
reduced. Therefore, the microwave noise is effectively grounded to
shielding case 100 so as to be completely dissipated.
When using the conventional through-type capacitor or the Jun's
capacitor, the through conductors, the electrode connectors and the
fastening tabs are separately formed. When manufacturing a
capacitor by assembling these components, after perpendicularly
fixing an electrode connector to a through conductor, the through
conductor is inserted in the through hole of the ceramic
dielectric. Then, an insulation resin material is filled in the
through hole. In such a case, due to many components of the
capacitor, the assembling work is increased to lower the
productivity.
Further, when the concentricity of the electrode connector and the
through conductor are not coincident, it is difficult to maintain
the perpendicularity of the through conductors with respect to the
ceramic dielectric in the through holes. FIG. 7A is a view for
illustrating the state that through conductors 146 of Jun's
capacitor do not maintain the perpendicularity so that each of
through conductors 146 is inclined at an angle of .theta. with
respect to the central axis of through hole 134. This is due to the
poor perpendicularity of each of through conductors 146 with
respect to electrode connector 150 as shown "A" in FIG. 7A. In such
a case, the thickness of the insulation resin material filled
between the inner surface of through holes 134 and through
conductors 146 is not uniform (that is, the thickness of the portio
"B" is thinner than the other portions), thereby lowering the
voltage resistance of the capacitor and providing a poor appearance
as well.
Further, there is possibility that a gap may be formed between the
electrode connectors and the separate electrodes so that the
interfacial state therebetween becomes poor. FIG. 7B shows the poor
interfacial state generated by the gap "G" between electrode
connector 150 and separate electrodes 136. In such a case, the
capacitance of the capacitor is varied so that the voltage
resistance of the capacitor is lowered. Further, there is a
difficulty in filling the first and second insulation resin
materials in the above insulation case and insulation cylinder.
SUMMARY OF THE INVENTION
The present invention is intended to overcome the above described
disadvantages. That is, it is an object of the present invention to
provide a noise shielding apparatus for the magnetron of a
microwave oven, in which the lowering of the voltage resistance and
the capacitance of the capacitor due to the poor concentricity and
the poor interfacial state may be prevented.
Another object of the present invention is to provide a noise
shielding apparatus for the magnetron of a microwave oven, in which
the structure is relatively simple, so that the material cost would
be saved, and that the productivity would be improved.
For achieving the above object, the noise shielding apparatus
according to the present invention includes:
a shielding case having a side wall with an elliptic opening and
having a projected portion formed along the elliptic opening by
bending out a circumference portion of the elliptic opening, and a
recess formed on an inner surface thereof corresponding to the
projected portion;
an elliptic cylindrical ceramic dielectric having a size
corresponding to the elliptic opening of the shielding case, and
having a pair of through holes;
a pair of separate electrodes separately formed on an upper surface
of the ceramic dielectric;
a common electrode formed on a lower surface of the ceramic
dielectric and oppositely from the separate electrodes;
a pair of through conductors passing through the through holes and
connected to a choke coil of the magnetron, each of the through
conductors being provided with an electrode connection portion for
electrically connecting with the separate electrodes, the electrode
connection portion being integrally and horizontally formed from
around an upper portion of each of the through conductors;
an insulation case with a lower portion secured on the projected
portion of the shielding case for surrounding the ceramic
dielectric; and
an elliptic insulation cylinder with its upper portion secured in
the recess of the shielding case for surrounding the through
conductors.
In accordance with one embodiment of the present invention, the
electrode connection portion is formed in a ring shape along a
periphery of each of the through conductors by horizontally
extending from each of the through conductors. Preferably, a
recessed portion is formed on a bottom of the electrode connection
portion for stably filling into the through holes and the recessed
portion is formed between each of the through conductors and an
outer periphery of the electrode connection portion. Also, a
bending portion is preferably formed at the outer periphery of the
electrode connection portion for increasing a contact area between
the electrode connection portion and the separate electrodes and
for improving a stable perpendicularity of the through
conductors.
According to another embodiment of the present invention, an
insulation lattice is formed at a central upper portion of the
insulation case over a border line of the separate electrodes.
The present invention further provides a noise shielding apparatus
for a magnetron, comprising:
a shielding case having a side wall with an elliptic opening and
having a projected portion formed along the elliptic opening by
bending out a circumference portion of the elliptic opening, and a
recess formed on an inner surface thereof corresponding to the
projected portion;
an elliptic cylindrical ceramic dielectric having a size
corresponding to the elliptic opening of the shielding case, and
having a pair of through holes;
a pair of separate electrodes separately formed on an upper surface
of the ceramic dielectric;
a common electrode formed on a lower surface of the ceramic
dielectric and oppositely from the separate electrodes;
a pair of through conductors passing through the through holes and
connected to a choke coil of the magnetron, each of the through
conductors being provided with an electrode connection portion for
electrically connecting with the separate electrodes, the electrode
connection portion being integrally and horizontally formed from
around an upper portion of each of the through conductors, the
electrode connection portion having a recessed portion formed on a
bottom of the electrode connection portion for stably filling into
the through holes, the recessed portion being formed between each
of the through conductors and an outer periphery of the electrode
connection portion;
an insulation case with a lower portion secured on the projected
portion of the shielding case for surrounding the ceramic
dielectric;
an elliptic insulation cylinder with its upper portion secured in
the recess of the shielding case for surrounding the through
conductors;
a first insulation resin material filled within the insulation case
so as to surround the ceramic dielectric;
a second insulation resin filled in an upper portion of the
insulation cylinder so as to surround the through conductors;
a fastening tab formed on an upper portion of each of the through
conductors for being connected to an external terminal, and the
fastening tab being extended outside of the insulation case;
and
a pair of insulation tubes surrounding a pair of the through
conductors, respectively. Preferably, the insulation tubes are
buried with the second insulation resin material. An insulation
lattice may be formed at a central upper portion of the insulation
case over a border line of the separate electrodes. Here, the lower
end of the insulation lattice is buried with the first insulation
resin material. Further, the insulation lattice is preferably
formed between a pair of the fastening tabs so as to have an upper
end with a height higher than the height of the fastening tabs.
The shielding case is protrudingly bent so as to form a projected
portion around the opening. Since a separate ground fitment is
unnecessary, the material cost is saved, and a working process for
installing the ground fitment is unnecessary, thereby improving the
productivity.
Further, in replacement of the electrode connector an electrode
connection portion is integrally formed with the through
conductors, which prevents the poor perpendicularity and/or poor
interfacial state which arise when assembling a separate electrode
connecter with the through conductors. Providing the insulation
lattice solves simply and stably the insulation problem between
fastening tabs and thus the magnetron may be stably operated.
The microwave noise which is generated by the magnetron is
continuously dissipated by the ceramic dielectric during passing
through through conductors which are inserted in the ceramic
dielectric. The noise is completely dissipated by being grounded to
shielding case 201 which is connected to common electrode.
In the present invention, since the conventional holes for securing
the ground fitment to the shielding case are unnecessary, the
leakage of the microwave noise through the four holes of the
shielding case is prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
The above objects and other advantages of the present invention
will become more apparent by describing in detail a preferred
embodiment thereof with reference to the attached drawings in
which:
FIG. 1 is an exploded perspective view of a noise shielding
apparatus including a conventional through-type capacitor;
FIG. 2 is a front sectional view of the through-type capacitor of
FIG. 1;
FIG. 3 is a partial sectional view for illustrating a magnetron
having a conventional through-type capacitor;
FIGS. 4A and 4B are respectively a partial front view and a partial
sectional side view for explaining the noise leakage in a noise
shielding apparatus having a conventional through-type
capacitor;
FIG. 5 is an exploded perspective view of a capacitor disclosed in
the prior U.S. patent application;
FIG. 6 is a front sectional view of the noise shielding apparatus
of FIG. 5;
FIG. 7A is a view for illustrating the state that the through
conductor of Jun's prior capacitor does not maintain the
perpendicularity;
FIG. 7B shows the poor interfacial state generated by the gap "G"
between the electrode connector and the separate electrodes;
FIG. 8 is an exploded perspective view of a noise shielding
apparatus for a magnetron according to one embodiment of the
present invention;
FIG. 9 is a front sectional view for illustrating the combined
state of the noise shielding apparatus of FIG. 8;
FIG. 10 is a side sectional view for illustrating the combined
state of the noise shielding apparatus of FIG. 8;
FIG. 11 is an enlarged sectional view enlarging the capacitor
portion of FIG. 9;
FIG. 12 is a partial sectional view for showing the state that each
of the through conductors according to one embodiment of the
present invention is fixed on each of separate electrodes;
FIG. 13A is a front view of a through conductor as shown in FIG.
12, FIG. 13B is a partial sectional view of the upper portion of
the through conductor as shown in FIG. 13A and FIG. 13C is a bottom
view of the through conductor as shown in FIG. 13A;
FIG. 14A is a front view of a through conductor according to
another embodiment of the present invention, FIG. 14B is a partial
sectional view of the upper portion of the through conductor as
shown in FIG. 14A and FIG. 14C is a bottom view of the through
conductor as shown in FIG. 14A;
FIG. 15 is a partial perspective view for showing a state that
wiring tabs of the wirings for the power supply are connected to a
magnetron having a noise shielding apparatus according to one
embodiment of the present invention; and
FIGS. 16A and 16B are respectively a partial front view and a
partial sectional side view for showing a magnetron wherein a noise
shielding apparatus having a through-type capacitor according to
one embodiment of the present invention is applied.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Hereinafter, the present invention will be described in detail
referring to the accompanying drawings.
FIG. 8 is an exploded perspective view of a noise shielding
apparatus for a magnetron according to one embodiment of the
present invention, FIG. 9 is a front sectional view for
illustrating the combined state of the noise shielding apparatus of
FIG. 8, FIG. 10 is a side sectional view for illustrating the
combined state of the noise shielding apparatus of FIG. 8 and FIG.
11 is an enlarged sectional view enlarging the capacitor portion of
FIG. 9.
The shown noise shielding apparatus includes a through-type
capacitor 230 which is similar to the conventional capacitor.
Capacitor 230 includes an elliptic ceramic dielectric 232, and
ceramic dielectric 232 is provided with a pair of vertical through
holes 234 which are substantially parallel with each other.
Further, a pair of mutually separate electrodes 236 are provided on
the top (the upper surface) of ceramic dielectric 232, while a
common electrode 238 is provided on the bottom (the lower surface)
of ceramic dielectric 232. Separate electrodes 236 and common
electrode 238 are provided with the through holes corresponding to
through holes 234 of ceramic dielectric 232.
Capacitor 230 is secured to a shielding case 201 which is provided
with an elliptic opening 211 at a center portion of a side wall
thereof for receiving capacitor 230. Further, an opening 300 is
formed at a center portion of an upper portion of shielding case
201 for receiving the cathode terminal of a magnetron, while the
lower portion of shielding case 201 is totally open. A projected
portion 210 is integrally formed with a proper height around
opening 211 by protrudingly bending a circumference portion of
opening 211. On an inner surface portion of shielding case 201, a
recess 213 is formed corresponding to projected portion 210. Around
projected portion 210 and on the surface portions of shielding case
201, there are formed reinforcing ribs 212 for reinforcing the
strength of shielding case 201.
Ceramic dielectric 232 is secured to projected portion 210 of
shielding case 201 by fixing common electrode 238 to projected
portion 210 by a proper means such as soldering or the like. The
surface of common electrode 238 is directly contacted with the
surface of projected portion 210 of shielding case 201 so that the
ground resistance is reduced. At this time, the surface of
projected portion 210 of shielding case 201 or the whole upper
surface of shielding case 201 including projected portion 210 is
preferably plated with tin. In such a case, when common electrode
242 is fixed by soldering, the binding force increases and the
contact resistance can be minimized so that the capacitor's
function is increased.
Capacitor 230 includes a pair of through conductors 246 each
surrounded by an insulation tube 248 which is made of a proper
material such as silicon. Through conductors 246 are disposed at a
center portion of shielding case 200, and are connected to a choke
coil which is connected to the filament of the magnetron, and
connecting through conductors 246 with the filament can be
performed by a proper means such as soldering or the like.
Each of through conductors 246 is integrally provided with each of
fastening tabs 262 to which a high voltage is applied. Fastening
tabs 262 are received into insulation case 254, so that an end
portion of fastening tabs 262 would project from insulation case
254, thereby making it easy to be connected to an external
terminal.
Further, at an upper portion of through conductors 246 an electrode
connection portion 250 is integrally formed. Electrode connection
portion 250 performs the role of the electrode connector (50 of
FIG. 1 and 150 of FIG. 5) of the prior capacitor. Electrode
connection portion 250 is integrally formed by horizontally
extending from around fastening tabs 246 in a ring shape so that
through conductors 246 are electrically connected with separate
electrodes 236 via electrode connection portion 250. Through
conductors 246 each integrally provided with electrode connection
portion 250 and fastening tabs 262 may be formed by forge using a
heading machine or the like.
Insulation tubes 248 are inserted into through holes 234. Fixing
through conductors 246 to through holes 234 can be performed by
fixing each of electrode connection portion 250 on each of separate
electrodes 236 using a proper means such as soldering or the
like.
Since each of electrode connection portions 250 is integrally
formed with each of through conductors 246, the coinciding the
central axis of each of through conductors 246 with the center line
of each of through holes 234 may be easily performed.
FIG. 12 is a partial sectional view for showing the state that each
of through conductors 246 according to one embodiment of the
present invention is fixed on each of separate electrodes 236. As
shown in the figure, when fixing each of through conductors 246 of
an integral type according to the present invention in which each
of through conductors 246 is integrally provided with electrode
connection portion 250, the concentricity of each of through
conductors 246 with each of through holes 234 and the
perpendicularity of electrode connection portion 250 with respect
to the center line of through holes 234 can be maintained
uniformly.
FIG. 13A is a front view of a through conductor 246 as shown in
FIG. 12, FIG. 13B is a partial sectional view of the upper portion
of through conductor 246 as shown in FIG. 13A and FIG. 13C is a
bottom view of through conductor 246 as shown in FIG. 13A. As shown
in these figures, electrode connection portion 250 is formed at an
upper portion of each of through conductors 246 in a ring shape by
horizontally extending along the outer periphery of each of through
conductors 246. Preferably, at the bottom of electrode connection
portion 250, a ring-shaped recessed portion 251 is formed between
the outer periphery of electrode connection portion 250 and each of
through conductor 246. Forming ring-shaped recessed portion 251 in
this way enables an insulation resin material to be stably filed in
through holes 234.
FIG. 14A is a front view of a through conductor 246 according to
another embodiment of the present invention, FIG. 14B is a partial
sectional view of the upper portion of through conductor 246 as
shown in FIG. 14A and FIG. 14C is a bottom view of through
conductor 246 as shown in FIG. 14A. The through conductor as shown
in FIGS. 14A to 14C is the same as shown in FIGS. 13A to 13C except
for a bending portion 250a. The same reference numerals in FIGS.
14A to 14C denote the same members as in FIGS. 13A to 13C. Bending
portion 250a is formed by being extended from the outer peripheral
portion of electrode connection portion 250 having ring-shaped
recessed portion 251 at the bottom thereof. Forming bending portion
250a in this way increases the contact surface area between
electrode connection portion 250 and each of separate electrodes
236 and improves the stability when fixing through conductors
246.
Capacitor 230 also includes an insulation case 254 and an
insulation cylinder 256. The lower portion of insulation case 254
which surrounds ceramic dielectric 232 is secured on projected
portion 210, while the upper portion of insulation cylinder 256
which surrounds through conductors 246 is secured in recess 213 of
shielding case 201. Insulation case 254 is filled with a first
insulation resin 258 such as an epoxy resin so as to cover an
outside ceramic dielectric 232 to thereby ensure its moisture
proofness and its insulation properties.
Further, the upper portion of insulation cylinder 256 and the space
between insulation tubes 248 and the inner surface of through holes
234 are filled with a second insulation material 256 comprised of
the same insulation resin material as first insulation resin
material 258. Insulation case 254 and insulation cylinder 256 are
comprised of a thermoplastic resin such as PBT.
In the conventional through-type capacitor as shown in FIGS. 1 and
2, insulation tubes 48 are partially exposed to the outside of
second insulation resin material 60. In the present invention,
through conductors 248 may be formed in this way. However, when
insulation tubes 48 are exposed to the outside of second insulation
resin material 60 as in the prior art, moisture may penetrate into
the insulation resin material through the gap formed between
through conductors 46 and insulation tubes 48. Therefore, in the
present embodiment, insulation tubes 248 are preferably made short
so that the lower ends thereof is lower than common electrode 238
of ceramic dielectric 232 which is being buried by second
insulation resin material 256. Forming insulation tubes 248 in this
way enables the insulation resin material to fill the gap between
insulation tubes 248 and through conductors 246 so that penetration
of the moisture through the gap may be prevented. Therefore, the
insulation characteristics of the insulation resin material is
improved.
Further, capacitor 230 includes an insulation lattice 261 having a
predetermined height at a center upper portion of insulation case
254. Referring to FIG. 11, when first insulation resin material 258
is filled inside insulation case 254, the lower end of insulation
lattice 261 is buried by first insulation resin material 258.
Insulation lattice 261 is disposed above the border line of
separate electrodes 236 and the lower end thereof does not contact
with ceramic dielectric 232 and the upper portion thereof is
exposed to the outside of insulation case 242 by a predetermined
height.
Insulation lattice 261 is disposed between a pair of fastening tabs
262 formed at the upper ends of a pair of through conductors 246.
When connecting the wiring tabs provided at the ends of the wires
for power supply with fastening tabs 262, insulation lattice 261
effectively prevents the interference between the wiring tabs.
FIG. 15 is a partial perspective view for showing a state that
wiring tabs 700 of the wirings 600 for the power supply are
connected to a magnetron having a noise shielding apparatus
according to one embodiment of the present invention.
Providing insulation case 254 with insulation lattice 261 in this
way effectively prevent the interference between two tabs 700 of
the wirings when connecting tabs 700 with fastening tabs 262.
Therefore, two wiring tabs 700 can be safely connected to fastening
tabs 262 without the necessity of additional insulation sleeve or
housing for insulating these wiring tabs 700. Here, insulation
lattice 261 is preferably formed so as to have a predetermined
height slightly higher than the top ends of wiring tabs 700. The
insulation lattice is preferably comprised of the same material as
insulation case 254 so that the insulation lattice and insulation
case 254 may be molded simultaneously. However, insulation lattice
261 may be manufactured by using a different insulation material
from that of insulation case 254 and then insulation lattice 261
may be adhered to the upper portion of insulation case 254 by using
an adhesive.
FIGS. 16A and 16B are respectively a partial front view and a
partial sectional side view for showing a magnetron wherein a noise
shielding apparatus having a through-type capacitor according to
one embodiment of the present invention is applied.
In the case where the noise shielding apparatus of the present
invention is used, if a microwave noise which is generated from the
magnetron flows in reverse, the microwave noise passes through the
choke coil which is connected to the filament of the magnetron,
cathode stem 802 and cathode terminal 804 with the result that a
portion of the noise is offset owing to the reactance of the coil.
The rest of the microwave noise passes through through conductors
246 which are connected to the choke coil, and during this passing,
a portion thereof is dissipated by the capacitor which includes
ceramic dielectric 232 (in which through conductors 246 are
inserted). The last remaining portion of the noise is completely
dissipated by being grounded to shielding case 201 which is
connected with common electrode 238.
In the present invention, shielding case 201 is protrudingly bent
so as to form projected portion 210 around opening 211. Projected
portion 210 performs the role of the conventional ground fitment
(40 in FIG. 1) which is fixedly installed on the shielding
case.
Since projected portion 210 effectively performs the role of the
conventional ground fitment 40, a separate ground fitment is
unnecessary. Therefore, the material cost is saved, and a working
process for installing ground fitment 40 is unnecessary, thereby
improving the productivity.
Further, in replacement of electrode connector (50 of FIG. 1 and
150 of FIG. 150), electrode connection portion 250 is integrally
formed with through conductors 246, which prevents the poor
perpendicularity and/or poor interfacial state which arise when
assembling a separate electrode connecter with the through
conductors. Therefore, the capacitance variance and bad effects on
the voltage resistance of the capacitor may be avoided and the
assembling work is reduced and the number of the components
decreases as well.
Further, providing the insulation lattice solves simply and stably
the insulation problem between fastening tabs and thus the
magnetron may be stably operated.
The microwave noise which is generated by the magnetron is
continuously dissipated by ceramic dielectric 232 during passing
through through conductors 246 which are inserted in ceramic
dielectric 232. Then, the noise is completely dissipated by being
grounded to shielding case 201 which is connected to common
electrode 238. In the present invention, when compared to a
conventional apparatus, projected portion 210 which performs the
role of the conventional ground fitment is integrally formed on
shielding case 201. Therefore, the surface of common electrode 238
of ceramic dielectric 232 directly contacts with the surface of
projected portion 210, and therefore, the grounding resistance is
reduced. Therefore, the microwave noise is effectively grounded to
shielding case 201 so as to be completely dissipated.
Further, according to the present invention, the conventional holes
for securing ground fitment 40 to shielding case 201 are
unnecessary. On the other hand, in the conventional apparatus, when
the ground fitment is secured to the shielding case, the shielding
case has to be provided with four fastening holes, and therefore,
the microwave noise is leaked through the four holes of the
shielding case. Therefore, in the present invention unlike the
conventional apparatus, there is no possibility that noise may leak
through the four holes of the shielding case.
Further, forming reinforcing ribs 212 around projected portion 210
improves the strength of shielding case 201.
While the present invention has been particularly shown and
described with reference to particular embodiments thereof, it will
be understood by those skilled in the art that various changes in
form and details may be effected therein without departing from the
spirit and scope of the invention as defined by the appended
claims.
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